Bicycles with multi-speed drives, such as the typical so-called ten speed bicycle, employ a coupling arrangement between the rear sprocket assembly and the rear wheel which transmits only forward rotation of the rear sprocket assembly to the rear wheel. This arrangement precludes the employment of a so-called coaster brake historically used on single speed bicycles in which a reverse rotation of the rear sprocket applies a brake built into the hub of the rear wheel. Bicycles which employ a multi-speed chain and sprocket system almost invariably employ caliper brakes which engage the wheel rims and are actuated, through a cable connection, by a hand lever mounted on the handle bars of the bicycle.
Both the simple pedal actuated coaster brake and the hand lever actuated caliper brake are manually applied by the rider. While the rider may use his entire weight in applying a pedal actuated brake, the maximum brake applying force the rider can apply to a hand lever actuated caliper brake is represented by the strength of the riders hand grip. Because, in an emergency situation, the rider may be required to evasively steer the bicycle while applying the brake, controlled application of the brake by a handle bar mounted hand lever while steering to avoid a collision requires substantial skill on the part of the rider.
This problem has been recognized in the art, and various arrangements for pedal actuated braking systems for multi-speed chain drives have been proposed. Foster U.S. Pat. No. 3,966,229 discloses, in one embodiment, such a system in which a pivoted pawl is held clear of the path of movement of the main sprocket teeth during forward rotation of the main sprocket and is pivoted into underlying engagement with a tooth on the main sprocket upon reverse rotation of that sprocket. The pawl is mounted upon a lever which is driven downwardly by the pawl upon reverse rotation of the main sprocket and this downward movement of the lever is applied to tension the cable(s) of a conventional caliper type brake system.
While the basic concept proposed by Foster of transmitting reverse rotation of a pedal driven sprocket to a lever which will apply a cable actuated brake is feasible, the specific mechanical arrangement for accomplishing this purpose, disclosed in the aforementioned Foster patent, has certain drawbacks. The pawl in the Foster system is positioned by a member which frictionally grips opposed sides of the main sprocket to maintain the pawl in a position clear of the sprocket during forward rotation and to draw the distal end of the pawl toward the path of the main sprocket teeth upon reverse rotation of the main sprocket. Because this member is frictionally engaged with the main sprocket at all times, it is subject to wear which can result in the loosening of the frictional grip of the member upon the sprocket. Because this gripping member engages the smooth sides of the sprocket, shifting of the pawl into engagement with the sprocket teeth is not synchronized with the movement of the sprocket teeth. This can result in the pawl tip striking the tip portion of a sprocket tooth and rebounding away from the sprocket. Further, in order to accommodate entry of the pawl tooth into the space between two teeth of the sprocket, the tip of the pawl must be relatively narrow, and the entire brake applying force exerted by reverse rotation of the sprocket is applied to this relatively narrow tip portion.
These last problems are by the present invention.